A ray-tracing simulation was performed to explore whether the interactions between tides and oppositely-propagating waves could explain the observed double-layer structure of large N2/strong wind shear. It is found, using the GROGRAT model, that tidal modulation has two effects on the wave propagation: (1) wave breaking levels descend at a tidal phase. (2) breaking levels for oppositely-propagating waves are separated by ∼10 km. The model results are qualitatively very similar to the observations.